Lifting magnet



Aug. 3 1926. 1,594,567

J. E. SEDERHOLM LIFTING MAGNET [NVE/V TOR JOHN T dfpfRHoLp/l iTroR/vfnsPatented Aug. 3, ,1926,

UNITD sTATizS learn'NT oF JOHN E. SEDEBHOLII, OF ST.PAUL,MINNESOTA,.ASSIGNOR TO AMERICAN HOIST .&

1,594,567 FICE.

DERRICK COMPANY, A; PARTNERSHIP COMPOSED 0F F. J. JOHNSON AND W. O.WASHBURN, 0F ST. PAUL, yIllllIINNIESO'lA.

LIFTING MAGNET.

Application led February 15, 1926. Serial No. 88,346.

This invention relates to improvements in lifting magnets,-the generalobject of the invention being to produce a cheap andl ellicient magnet,of the cylindricalcase type, wherein there are no joints in the magneticcircuit. f

It is well known that when a lconnection is to be maintained in anelectric circuit, the contact between the joined elements must beperfect to prevent localization effects. In a device like a liftingmagnet which is subject to hard usage, the parts are of such magnitudeand the meeting surfaces ofthe joined elementsareof such area, thatjoints cannoty be properly securely soldered or welded to obtain andmaintain perfect contact'. This is particularly true of magnets havingpole shoes, wherein the maintenance .of proper contact between thepoleshoe and magnet case is .practically impossible, inasmuch aspounding action against the shoe breaks vthe joint, reduces contact andcauses localization effects, which materially reduce the efficiency oftheA magnet.

An object of the invention, therefore, is to construct` a cylindricalliftin magnet, Without the use of a pole shoe, an to secure and sealrthecoils within the magnet case without producing a joint in the magneticcircuit, thus eliminating the use of pole shoe structure and attendantlocalization effects.

`Qther objects are to obtain a uniform magnetic flux density through themagnetic circuit; to reduce the number of parts; to seal t-he coilsagainst moisture;` to provide non-joint means for securing the coils inthe case; ftogive maximumA working surfaces with minimum .of size andweightfof magnet case ory frame; to reduce the weight and size of thedevice as a. whole; to secure brace and reinforce the coils to preventvibration; and. tosupoort a coil retaining plate againstbreakage,whenlthe magnet is dropped.

Features of the invention include a coil retaining plate and non-jointring-lock for the same, adaptedtosecure theplatewithinaicoilsreceivinggroove and to seal the coils againstmoisture. .c

Other features Include the .of suppontnglhe .coilfretainingplate againstabrgakgeladithfhoidipg,anche con in fixed invention will be disclosedinthe description of the drawings, and in said drawings.

Figure l is a vertical diame-tric'section taken through the coilconnector means;

.Figure 2 is a plan view of the device viewing the lower or workingface,l with parts broken away to show the reinforcing and spacing rodsfor the coil-retaining plate and coils;

Figure 3 is an enlarged detail of the seal and lock device, for thecoil-retaining plate; and

Figures 4 and 5 are views of the rings.

The numeral l designates a soft iron onepiece cylindrical magnet case orframe, having a flat working face 2 and further having a circularcoil-receiving and housing groove 3, .extending inwardly from and atright angles to the working' face concentrically with the axis of thecylindrical case. This groove defines and provides an annular or hollowcylindrical flange, 4., of substantially uniform magnetic capacityaxially and circumferentially of the case, and a central cylindricalboss or post 5, of substantially the same magnetic capacity or cubicalcontent as the fiange, or of` such cross Section as to provide wellbalanced magnetic capacity relation between lange and boss.

A novel. non-joint coil-retaining locking andsealing means is providedin the following manner.: The coil groove 3 is provided with outwardlyfaced circular shoulders respectively 6 and 7, at each side, the'shoulders being parallel with each other aligned crosswise of the grooveand parallel to the working face 0f the case or. frame. In this case twoannular coils respectively 8, 9, are used, which are disposedwithin andagainstthe bottom side of the groove 3. The com bined width of the coilsisfless than the width of the groove, and a number of brace elements,10, as posts, are inserted between the coils in circumferential spacedrelation and held so spaced by suitable insulating material` `13, suchasasbestos The Vfunction of these lposts is to support a nonmagneticcoil retaining plate or shieldagain'st break` age .whenvthe magnet isdroppedf' This support particularly necessary, inasmuch as .the .widthofjtfherlannular plate4 'relatively great,l-be1ng from#j .twelve -toeighteen inches cialv sealing compound 11 designedto pre` vent sweating.rhe outer or louer faces of the coils are covered with a specially treated asbestos insulation indicated at lf2. rthe depth of the coil groeveinwardly from the shoulders is less than the corres}')onding dimensionof the coils so that the outer face of the asbestos insulation l2 issubstantially aligned with the shoulders.

Adjacent the shoulders outwardly therefrom are a pair of opposinglyrelated locking ring receiving grooves 14, 15, one in the flange and onein the boss, receiving steel-retaining rings indica at 16, 1T. Theserings are split to l their engagement, and act to .f-:ealii'igly engageand retain a single piece annular coilretaining member 1S ofnon-magnetic material, in this instance of manganese steel. The innerside of the member 1S engages the asbestos insulation 1:2, and shoulders(i, 7 in a manner to press the coils tightly and hold the same securelysealed `Within the groove, the inner 'faces of the retaining ringsengaged snugly against the outer suri'iaces of the member 1S, and thismember is thus forced inwardly to clamping and sealing position. Afterproper engagement, the opposing ends of the split portion of each ringis soldered, and the joints are callted at 2O to close the jointsbetvseen the ring and plate. rllhus the coils are non-vibratorilysecured, and sealed, vfitbout the use of bolts. and Without joints inthe magneticl circuits.

Connections for the coils may be made in any approved manner but theconstruction shoivn is preferred.

The numeral 25 indicates a terminal chamber Where the connections aremade With the plug terminal. The chamber is closed by cap plate 26suitably held by bolts 2T. and through this cap plate extend insulating`bushings 28 pressed through the cap plate. Bronze terminal connectorsQ9, tivo in number, are provided, one passing through each baltelitebushing. The upper ends of these members are split for obtaining africtional connection with the cable terminals, when the same areplugged in. Flexible terminal leads 30 connect the coils With theterminal connectors 29.

Numeral 31 indicates a protecting cast. steel casing for the terminals,which are held Within their bushings by suitable lock nuts 32. rIheusual chain lugs 34 are provided, three pairs arranged in equi-lateraltriangular relation, and projecting upvrardly from the top of themagnet.

The magnet case is recessed as at 35, which corresponds to the neutralZone of the magnet, the material being thus cut away to reduce theWeight of the device, Without in any Way affecting its lifting capacity.

llhen it is desired to remove the rings for any purpose the ringmay beeither cut G. Y, and spaced open by the flame of a blow torch, or bycold chisel, and when repairs have been made and the rings re-inserted,the same are simply again welded and call ed to force the metal of ringand plate into sealing engagement. Suitable cooling ribs are indicatedatv 36. .lt is to be noted that no flange circumferentially of theWorking face of the magnet is used, for if it were, part of the fieldstrength would be absorbed or Wealtened and the lifting capacity of themagnet would be reduced. rIhis would be specially so in handling scrapand pig iron, where only small contacts are made. A very evendistribution of force or maximum number of magnetic lines per squareinch is therefore essential, and is obtained and maintained in thepresent device.

By substantially insetting the outer surface of the manganese steelplate Within the groove, the quantitative capacity of the magnet is.somewhat increased, for lifting small articles such as steel shavingsor scrap, since a portion of the scrap enters the groove and is heldtherein by the outermost material vfhen the coils are energized.

Advantages obtained by applicants onepiece non-joint magnet case orframe, are: that the amount of machine Work is reduced by tivo-thirds:no bolts are used which can become loose, mashed or rusted; the liftingcapacity remains constant because there is no pole-piece and thereforeno hammering action against such piece or joint between pole-piece andcase. The coils are quickly and easily assembled or dis-assembled andare retained in Water-tight and air-tight, braced condition, thus makingfor a long life of the device. The active Working surface is greater inproportion to the outside diameter than in magnets noW in use, andtherefore the lifting capacity is increased, Without correspondingincrease in Weight.

Having thus described my invention what l claim aS new and desire tosecure by Letters Pat-ent is l. device of the class described,comprislig a one-piece cylindrical magnet case having a coil-receivinggroove therein, coils Within the groove, a non-magnetic retaining membersecuring the coils, and ring members securing the retaining member incoil-retaining position.

2. A. device of the class described, comprising a cylindrical magnetcase, a coil-rcceiving groove concentric with the axis of the case,coils Within the groove, a plate ivithin the groove retaining the coils,and ring means abuttingly engaging the walls of the groove and plate,and sealingly securing the plate.

3. A device of the class described, comprising a one-piececylindrical'magnet case of soft iron, having a single concentricallyrelated coil-receiving groove, concentric with the cylindrical axis ofthe case, each opposite wall of saidgroove having a shaln lowring-receiving groove, annular coils within the first mentioned grooveinset a Substantial distance from the working face, a non-magneticannular member for retaining the coils, and retaining ring elements,engaged within the shallow grooves, for securing the member and coils.

4. A device of the class described, comprising a cylindrical magnetframe, having a concentrically related annular coil groove, lockinggrooves in the walls of the coil groove, coils within the coil groove,an annular retaining plate for the coils disposed within the coilgroove, bracev elements Ibetween the coil and abutting groove and plate,and retaining and sealing rings within the locking grooves, sealinglyengaged with the retaining plate.

5. A device of the class described comprising a one-piece cylindricalmagnet case having a flat working face, and having a circular coilgroove concentric with the axis of the coil, said groove havingoutwardly faced circumferentially aligned shoulders spaced outwardlyfrom the bottom of the groove, and further having locking ring receivinggrooves adjacent and s aced outward- 1y from said shoulders, coilswithin and at the bottom of the first mentioned grooves, a coilretaining member of non-magnetic material engaged against the shouldersand coils spaeedoutwardly from said shoulders, coils within and at thebottom of the irst mentioned grooves, a coil-retaining member ofnon-magnetic material engaged against the shoulders and coils to securethe coils, and retaining rings engaged within the ring-receivinggrooves, clampingly and sealingly engaged against the retaining member.

G. A device of the class described, comprising a one-pies cylindricalmagnet case having a flat working face, and having a circular coilgroove, extending inwardly7 trom said working face, deiining andproviding an annular' lange of substantially uniform magnetic capacity,and a central cylindrical boss or post having substantially the samemagnetic capacity as the flange, said groove having outwardly facedcircumferential shoulders at each side aligned with each other in aplane parallel with they working face of the case, locking-ringreceiving grooves, adjacent said shoulders, one for each shoulder andspaced outwardluv,7 therefrom, coils within the groove inset from theslnmlders with their outer faces disposed inv-.fardly from the shoulder,insulating material between the coils and shoulders, an annularretaining ring of non-magnetic matcrial engage-d against the shouldersand insulating material to secure the coils, and a retaining ringsealingly engaged within each locking ring groove, and with the face ofthe non-magnetic annulus.

In witness whereof, I have hereunto set my hand this 10th day ofFebruary, 1926.

JOHN E. SEDERHOLM.

